The present invention pertains to a process of preparing an aqueous dispersion containing a pigment uniformly distributed throughout. In particular, the invention relates to a process of dispersing a pigment in an aqueous system with a styrenated and sulfated phenol ethoxylates. The invention is also directed to aqueous carbon black dispersions containing carbon black and surfactants based on sulfated styrenated phenol alkoxylates, in addition to water. The dispersions are produced by dispersing the carbon black and the other constituents in water, using bead mills, ultrasonic mills and/or an ultra-turrax. The aqueous carbon black dispersions can be used in many applications such as printing inks including ink-jet inks or writing inks. Also the carbon black dispersions are also useful in lubricating applications.
The present invention also relates to pigment dispersions free from organic solvents and containing a carboxymethylated styrenated phenol alkoxylate as dispersing agent. The pigment dispersion can be used in paints based on water as well as organic solvents.
The present invention also provides homogeneous pigment dispersions which are completely free from organic solvents and which, without causing flocculations which may cause unacceptable differences in color, may be used in water-based paints as well as paints containing organic solvents.
This invention also relates to pigment dispersions suitable for pigmenting hydrophilic as well as hydrophobic media. The present invention further relates to methods of preparing inorganic pigment dispersions useful in the manufacture of latex paints, and latex paints prepared therewith.
One of the most difficult pigments to disperse and stabilize in a waterborne coating formulations or rubber compositions is carbon black, because of its enormous surface area and high oil absorption. Additionally, especially where a conductive carbon black pigment is to be utilized, it is important that the reduction of the electrostatic properties be minimized, and that the other physical characteristics of the final coating are not deleteriously affected by the particular pigment dispersant employed.
The products commonly employed in the prior art as carbon black dispersants in coatings are salts of an acrylic acid copolymer, acetylenic diol surfactants, or polyalcohol ethers which fit into various classes of wetting and dispersing agents, (Calbo, Handbook of Coatings Additives, Dekker pg. 516). Such additives could be called on to function as more than a dispersant and can also act in one or more of the following ways: a) to prevent flocculation, b) to prevent hard settling, c) to improve jetness/color/gloss, d) to control viscosity, and/or e) to improve wetting of the base resin.
Various considerations are important in determining the usefulness of any additive as a dispersing agent for use with a carbon black or with other pigments, depending upon the product into which such a dispersion is to be incorporated. When used throughout this application the terms pigment(s) or pigment dispersion(s) are intended to encompass various materials which may be intended to impart either color and/or serve some other function, such as for example the use of carbon black in rubber where, in addition to adding color, such also acts as a reinforcing agent.
One of the most important considerations in determining whether a particular dispersant will be useful for use with a given pigment or pigments when such a pigment is to be used in a paint or coating composition is whether such a dispersant/pigment combination will or will not impart a conductive nature or characteristic to the dried paint film or coating into which it has been added.
The automotive industry is replacing and will continue to replace exterior metal body panels on vehicles with plastic and composite body panels. Some reasons for this change are weight reduction, flexibility of design, and lower tooling costs. The replacement of metal body panels by plastics and composites is not without difficulties.
One problem of note is the electrostatic spray painting of plastics. Electrostatic spray painting is the preferred manner of applying automotive topcoats. Spray painting normally gives the best appearance to the vehicle and the electrostatic technique assures the most economical use of the material. The problem arises because plastics do not paint well electrostatically unless a conductive primer is used.
Amongst the most important considerations for determining the utility of any dispersant to be used in conjunction with conductive carbon blacks are the following: the inherent rheological stability of the dispersion, both alone and when added to a formulated paint; resistance to flocculation of the carbon black/dispersant mixture and in the final paint or coating; and ability to achieve low viscosity at high pigment loadings.
The various prior art references of which the applicants are aware which relate to dispersing agents for pigment additives, such as carbon blacks, suffer from a number of shortcomings. The most significant shortcomings of the carbon black dispersants of the prior art, including those used for conductive carbon blacks, are: high levels of dispersant may be required which tends to detrimentally affect the physical properties of formulated paints, such as adversely affecting the resultant humidity resistance, yellowing upon exposure to UV light, loss of cure in melamine cross-linked systems, and other undesirable effects; inability to prevent reflocculation of carbon black, resulting in the loss of electrical conductivity in dried paint films; and incompatibility of the dispersant with the particular resin system selected for use in the final paint formulation.
Additionally, more and more paints are produced which are water-based and completely free from organic solvents, such as glycol ethers. When toning these paints to the desired colour, use is made to a great extent of pigment dispersions, which can be used both for water-based paint and for paint based on organic solvents. The pigment dispersions are normally composed of pigments, fillers, dispersing agents and an aqueous phase in the form of ethylene glycol, di- and triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol and glycerol. In most cases, the dispersing agent is a nonionic surface-active compound or a combination of nonionic and anionic surfactants. For environmental reasons, it is however desirable that the pigment dispersions are solvent-free.
The shortcomings of the prior art dispersing agents noted above may be overcome by employing certain sulfated and/or carboxymethylated styrenated phenol alkoxylates in accordance with the present invention.
It is a first object of the present invention to provide novel pigment dispersions incorporating novel surfactants.
It is another object of the instant invention to provide novel pigment dispersions containing surfactants based on sulfated styrenated phenol alkoxylates.
A further object of the invention is to provide novel carbon black dispersions containing novel surfactants.
A still further object of the invention is to provide novel carbon black dispersions incorporating sulfated styrenated phenol alkoxylates.
An additional object of the invention is to provide novel pigment dispersions incorporating sulfated styrenated phenol ethoxylates.
A still further object of the invention is to provide carbon black dispersions containing surfactants based on sulfated styrenated phenol ethoxylates.
An additional object of the present invention is sulfated styrenated phenol alkoxylates.
Another main object of the present invention is to provide pigment dispersions incorporating sulfated styrenated phenol ethoxylate/propoxylate surfactants.
Another object of the present invention is to provide carbon black dispersions incorporating sulfated styrenated phenol ethoxylate/propoxylate surfactants.
A still further object of the present invention is to provide graphite dispersions incorporating sulfated styrenated phenol ethoxylate/propoxylate surfactants.
An additional object of the invention is carbon black dispersions incorporating craboxymethylated styrenated phenol ethoxylate/propoxylate surfactants.
Still, an additional object of the present invention is carboxymethylated styrenated phenol alkoxylates.
Still, another object of the invention are pigment dispersions having a very high tinctorial strength and brilliance, an excellent levelness and covering power in opaque applications
These and other objects of the present invention will more readily become apparent from the description and examples which follow.
The present invention is directed to a pigment dispersion comprising: (a) a pigment; and (b) an anionic surfactant selected from the group consisting of surfactants having the formulae: 
wherein x=1-70; y=1, 2, 3; z=1-70 and M+ is selected from the group consisting of NH4+, Na+, and K+, C1-C4 alkyl ammonium, C1-C4 dialkylammonium, C1-C4 trialkylammonium, monoethanolammonium, diethanolammonium and triethanolammonium.
The instant invention is also directed to a coloring pigment dispersion which is free from organic solvents comprising: (a) 1.0-60% by weight of a coloring pigment; (b) 5-30% by weight of an anionic surfactant selected from the group consisting of surfactants having the formulae: 
wherein x=1-70; y=1, 2, 3; z=1-70 and M+ is selected from the group consisting of NH4+, Na+, and K+, C1-C4 alkyl ammonium, C1-C4 dialkylammonium, C1-C4 trialkylammonium, monoethanolammonium, diethanolammonium and triethanolammonium; (c) 20-75% by weight of water; and (d) 0-5% by weight of auxiliary additives selected from the group consisting of antifoaming agents, and nonionic surfactants.
The present invention is also directed to an aqueous carbon black dispersion comprising, in addition to water, the following components:
5 to 50% by weight of carbon black; and 0.5 to 30% by weight of an anionic surfactant selected from the group consisting of surfactants having the formulae: 
wherein x=1-70; y=1, 2, 3; z=1-70 and M+ is selected from the group consisting of NH4+, Na+, K+, C1-C4 alkyl ammonium, C1-C4 dialkylammonium, C1-C4 trialkylammonium, monoethanolammonium, diethanolammonium and triethanolammonium.
The dispersants of the present invention are manufactured by reacting a styrenated phenol alkoxylate of the formulae (i) or (ii) 
wherein x=1-70; y=1, 2, 3; z=1-70 with an equimolar amount of sulfamic acid in the presence of dicyandiamide as a catalyst. The reaction is conducted in a suitable reactor at a temperature range of about 100xc2x0-130xc2x0 C., more preferably at a temperature range of 110xc2x0-125xc2x0 C. and most preferably at a temperature range of 115xc2x0-120xc2x0 C.
In the case of the carboxymethylated derivatives, the styrenated phenol alkoxylate of formulae (i) and (ii) are reacted under alkaline conditions (KOH or NaOH) with chloroacetic acid at temperatures in the range of 100xc2x0-130xc2x0 C. In another embodiment, the alkoxylate is reacted with a strong base such as sodium hydride and the resulting sodium salt is then reacted with the chloroacetic acid followed by neutralization with a base selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, C1-C4 alkyl amines, C1-C4 dialkylamines, C1-C4 trialkylamines, monoethanolamine, diethanolamine and triethanolamine.
The styrenated phenol alkoxylates are intended to include compounds having the following chemical structures: 
The propoxylated as well as the mixed product ethoxylate/propoxylate are also intended to be included withinb the scope of the present invention.
The pigments which may be dispersed according to the invention may consist of organic as well as inorganic pigments. Suitable inorganic pigments are, for example, iron oxides, chromium oxides, titanium oxides, chromium titan yellow, carbon black and mixtures thereof. Organic pigments are, for instance, azo, phthalo, cyanide and quinacridon pigments and derivatives from thionindigo, dioxazine and mixtures thereof. Mixtures of organic and inorganic pigments are also suitable for making the dispersions of the present invention.
Pigment blacks with an average primary particle diameter of 8 to 80 nm, preferably 10 to 35 nm, and a DBP number of 40 to 200 ml/100 g, preferably 60 to 150 ml/100 g, can be used as the carbon black. In a preferred embodiment of the invention, gas blacks with an average primary particle diameter of 8 to 30 nm, preferably 10 to 25 nm, can be used.
The pigment dispersions according to the invention contain 1 to 65% by weight, preferably 30 to 50% by weight, of pigment, 2 to 35% by weight, preferably 5 to 30% by weight, of the sulfated styrenated phenol alkoxylate products, 0 to 20%, preferably 0 to 5%, of additional nonionic or anionic surface-active agents, 5 to 20% by weight of water-retaining agents and 15 to 40% by weight of water.
The pigment dispersion composition of the present invention is prepared by adding a pigment to an aqueous solution of a pigment dispersant, disaggregating and dispersing the pigment in the solution by means of a dispersing machine such as roll mill, ball mill or sand mill, diluting the resultant dispersion to a desired concentration and removing larger particles therefrom by way of centrifugation, Scharples-type centrifugation and filtration. If a desired particle-size distribution cannot be obtained by the first particle classification process, the dispersing process and particle classification process are repeated until the desired particle-size distribution is obtained. In most instances, if the proportion of particles impassable through a sieve having a mesh size of 300 nm is not greater than 30%, there is no need for particle classification. Thus, the pigment contained in the dispersion has a median particle size of not greater than 250 nm, preferably not greater than 200 nm with not greater than 30% of the pigment particles being impassable through the sieve having a mesh size of 300 nm.
Also, the pigment dispersion according to the invention can be produced by first preparing a pigment-free mixture of the surface-active compounds, the water, the antifoaming agents and any other additives, and subsequently adding the pigment portion which is dispersed in the mixture. The dispersion can be carried out by means of a dissolver or grinder, for instance a ball grinder or roller mill.
The pigment dispersions according to the invention can be employed for all purposes and are excellently suitable for the production of emulsion paints based on polyvinyl acetate, polyvinyl acetate copolymers, styrene-butadiene copolymers, polyvinyl propionates, acrylic and methacrylic acid ester polymers, saponified alkyd resins and oil emulsions; for the production of wallpaper paints based on cellulose derivatives such as methylcellulose, hydroxymethylcellulose and carboxymethylcellulose, and for the production of printing inks which contain, as binders, mainly saponified natural resins, such as shellac, saponified water-soluble synthetic resins or acrylate binder solutions.